Alpha copper alloys



Patented June 24,1947

ALPHA COPPER ALLOYS Alan U. Seybolt, Columbus, Ohio, assignor, by. mesne assignments, to Electro Metallurgical Company, a corporation of West Virgin a No Drawing; Application October 15, 1941,

Serial No. 415,039

The invention relates to copper and copper base alloys in which the matrix or continuous phase is an alloy of the alpha copper type such as an alpha brass, or an alpha bronze.

In general, alloys of the alpha copper type have a face centered cubic crystallographic structure similar to that of copper. Alpha brasses may contain up to about 40% zinc and usually contain 25% to 40% zinc, the remainder substantially all copper. Alpha bronze may contain up to about 12% or tin, and usually contains at least about 2% tin. Small proportions of one or more 4 Claims. (Cl. 75.153)

of the elements manganese, silicon, lead and phosphorus may be added to alpha brasses or alpha bronzes to raise their corrosion resistance, strength, or both.

Articles composed of copper and alpha copper alloys are usually fabricated by cold working. The cold working operations cause the materials to be hardened to a substantial extent, but they 1 extent upon cold working that it is necessary to I anneal it between stages of the working operations to achieve the desired reduction in section; but the fact that these materials are readily softened is a disadvantage in that it limits their use for articles which maybe heated.

There is a demand for an alpha copper alloy which, even when heated to temperatures normally suflicient to fully soften cold worked alpha copper alloys, retains to a high degree the hardness produced by cold working and also is resistant to grain growth at high temperatures. It is an object of this invention to provide such an alloy. Another object is a method of raising the recrystallization temperature of cold worked alpha copper alloys, and a third object is a method of inhibiting grain growth of such materials on exposure to elevated temperatures. A further object is a cold worked article composed of an alpha copper alloy, which article retains its strength when exposed to elevated temperatures, for instance during a brazing operation or during use at high temperatures.

These objects are achieved by the invention which comprises an alpha copper alloy containing a small proportion of columbium which is effective to raise substantially the recrystallization and softening temperatures of the alloys and to inhibit grain growth in the alloys onexposure to elevated temperatures between about 200 C. and about 800 C. The invention also includes a method of raising the recrystallization and softening temperaturesv of. cold worked alpha copper alloys. and of inhibiting grain growth of suChalloys, which method comprises incorporating columbium in such alloys. Further, the invention 7 includes articles composed of columbium-containing alpha copper alloys.

' In accordance with the-invention there is added to copper or an alpha copper alloy about 0.02% to 1.5% of columbium. 'Preferably, the columbium is in a proportion between about 0.1% and 0.8%. Aluminum somewhat enhances the effects of the columbium, and is preferably present in a proportion between 0.1% and 1%. When both columbium and aluminum are used, these elements may be incorporated into the copper or alpha copper alloy by the use of a columbium-alu...

-minum pre-alloy containing about 20% to 50%.

columbium, the remainder substantially aluminum. When columbium alone is to be added, it is preferably added by means of a copper-columbium pre-alloy. The pre-alloys may also contain a minor percentage (up to about 25%) of iron, and small amounts, say up to 5% each, of silicon and carbon.

Tests have indicated-that a small proportion of columbium or of a mixture of columbium and aluminum has a pronounced effect in raising the recrystallization and softening temperatures of copper or alpha copper alloys and also reduces the rate of softening. In these tests, specimens of substantially pure copper and alpha copper, alloys. containing no columbium or aluminum and of copper and alpha copper alloys to which difierent proportions of columbium or a mixture of columbium and aluminum had been added were reduced 50% or by cold working, tested for hardness, heated for 30 minutes at each of several different temperatures (a different sample being used for each temperature), and again tested for hardness.

Whereas the softening temperature (after heating for one-half hour) of cold rolled substantially pure copper is between 200 C. and 300 C., the softening temperature of copper to which had been added 0.58% columbium was observed to be between 400 C. and 500 C. Similar mates Rockwell F hardness numbers of alpha coplpercolumbium allot/s cold-worked 50% as golglrolled and after heating 30 minutes at temperature Per As Cent Cold- 200 0. 300 0. 400 0. 500 0. 600 C. 700? 0. Oh rolled None 94 92 45 i 38 35 35 0.11 95 95 71 .45 41 42 38 0.16 92 92 92 69 47 45 i6 0. 21 92 92 90 8 56 48 0.58 95 95 95 94 62 55 56 0. 78 97 97 97 97 60 61 58 1 Alloy also contained 0.25% aluminum. gNdtest.

TABLE II Rockwell F hardness numbers of alpha brass alloys containing 35% zinc, 'co-ldeworked 50% as cold-rolled and after heating 30 minutes at temperature Per As Cent Cold- 250C. 300 .0. 400C}. 5099c. 5509; 600C.

o l a None 110 .110 95 81 7,0 s4 58 o. 035 no 110 97 s9 s4 s1 76 Microscopic examination of cold worked alloys of the invention indicated that they do not undergo recrystallization when heated at temperatures ordinarily sufficient to cause the recrystallization of similar alloys containing no columbiurn, i e. cold worked alloys within the composition limits of the invention have a fine grain structure which is retained even when the alloys are heated to elevated temperatures.

The alloys of the invention, because they possess the advantages of resisting grain growth and of retaining at elevated temperatures the strength and hardness produced by cold working, are well suited to use in the fabrication of articles exposed to elevated temperatures, such as vessels for hot fluids, for example condenser tubes, or of, deep drawn articles fabricated by successive drawing and annealing operations. A particularly useful application of the alloys of the invention is the fabrication of soldered articles. The strength and hardness of soldered articles composed of such alloys are substantially the same in areas at and adjacent the joint which have been heated during the soldering operation as they are at areas remote from the joint which have not been heated. Other uses to which they may be put will be apparent.

Although particular examples have been given herein of alloys of the invention, they are for the purpose of illustration merely, and the invention i net l m s te su examples- I claim:

1. Alpha copper brass alloy composed of copper, zinc and columbium, the zinc content being between 25% and 40%, the columbium content being between 0.02% and 1.5%, the remainder being substantially all copper; said alloy being ca bl 9 a enin b c ld wo kin a Characteri fid by its retention of the hardnessindu'ced by cold working upon exposure to elevated term peratures normally sufficient to soften cold worked copper brass alloys free from colurnbium.

elphawpee b ee l y eo m ed o c p tin and coluinbiurn, the tin content. being between and 15%Jth elllmb ilm ce e be n twe,en0.02% a1 1d'1.5%, the remainder being'subst antially all copper; said alloy being capable of hardening by cold working and characterized by its retention of the hardness induced by cold working upon exposure to elevated temperatures normally sufiicient to soften coldfworked copper bronze'alloys free from columbium.

,3- A ha s n a o emness l i omma columhium, the colurnbium content being between 9. 2 and the mainde f ub iall 'al eer r d'a lerbl lin at he h efn ns by sai w n in a d ehara t a i i its ree er; b the bushe ill-t e P s W rkle 1 9. 1 Osure t0 a d s p ratij r s re ma lv suite t9 eries 9 1 w ked we 4 re rom 91umt i a I 4- Ar; alpha server @093 f the a eas s n [of alloy se Qs d i e p r an mbium: an a l emne ed QI eha ras and c umb uma aliw s m as d 9 a ha renz and mb um: the ce umbi m fi ment Q fii a l b ing between 0-9 and 2 5%: eaislal b n mble 9 harden n by c ld W ki an b ng charact rized b its r tention .at le ate temperature o hardnes induced by su h col wo kinea empa ed wi simila a l ree em .q lumbiu n.

ALAN U. SEYBOL'I'. 

